Durring the 'End of The Line' update, some of the new 'torso' cosmetics ('Sleeveless in Siberia', 'Hunter Heavy' and the 'Coldfront Curbstompers') were unboxable in Unusual quality for a short period of time. This bug was patched after about 3 days. They have the, at that time, new unusual effects which would appear inside the player's stomach when in a game.

There are 4 instances of this item in Unusual quality.

Source